Gas sensor and nitrogen oxide sensor

Abstract

Disclosed are a gas sensor and a nitrogen oxide sensor each comprising a first diffusion rate-determining section for giving a predetermined diffusion resistance to a measurement gas to be introduced into a first chamber, the first diffusion rate-determining section being formed with a slit having a laterally extending aperture formed at a front end portion of a second spacer layer to make contact with the lower surface of a second solid electrolyte layer in which the aperture is formed to extend with an identical aperture width up to the first chamber, and a slit having a laterally extending aperture formed at a front end portion of the second spacer layer to make contact with the upper surface of a first solid electrolyte layer in which the aperture is formed to extend with an identical aperture width up to the first chamber. The slits have a substantially identical cross-sectional configuration, in which the length in the vertical direction is not more than 10 μm, and the length in the lateral direction is about 2 mm. Accordingly, it is possible to avoid the influence of the pulsation of the exhaust gas pressure generated in the measurement gas, and it is possible to improve the measurement accuracy obtained on the detecting electrode.

What is claimed is:  
     
       1. A gas sensor for measuring an amount of a measurement gas component contained in a measurement gas existing in an external space, said gas sensor at least comprising: 
       a substrate composed of a solid electrolyte to make contact with the external space;  
       an internal space formed at the inside of said substrate;  
       a gas-introducing port for introducing measurement gas from the external space into said internal space;  
       a diffusion rate-determining slit passage for introducing measurement gas from the external space into said internal space via said gas-introducing port under a predetermined diffusion resistance;  
       a buffering space provided between said gas-introducing port and said slit passage; and  
       a pumping means including an inner pumping electrode and an outer pumping electrode formed at the inside and outside of said internal space respectively, for pumping-processing oxygen contained in the measurement gas introduced from the external space, on the basis of a control voltage applied between said electrodes, wherein:  
       said slit passage has, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, and at least one dimension is not more than 10 μm; and  
       said buffering space has a cross-sectional area greater than that of said slit passage.  
     
     
       2. The gas sensor according to  claim 1 , wherein: 
       a clogging-preventative section and said buffering space are provided in series between said gas-introducing port and said internal space;  
       a front aperture of said clogging-preventive section is used to form said gas-introducing port; and  
       a diffusion rate-determining section for giving a predetermined diffusion resistance to said measurement gas is provided between said clogging-preventive section and said buffering space.  
     
     
       3. The gas sensor according to  claim 1 , wherein said oxygen contained in the measurement gas introduced from said external space into the internal space is pumping-processed by using said pumping means to make control so that a partial pressure of oxygen in said internal space has a predetermined value at which a predetermined gas component in the measurement gas is not decomposable. 
     
     
       4. The gas sensor according to  claim 3 , further comprising: 
       a measuring pumping means for decomposing said predetermined gas component contained in the measurement gas after being pumping-processed by said pumping means, by means of catalytic action and/or electrolysis, and pumping processing oxygen produced by said decomposition, wherein:  
       the predetermined gas component contained in said measurement gas is measured on the basis of a pumping current flowing through said measuring pumping means in accordance with said pumping process effected by said measuring pumping means.  
     
     
       5. The gas sensor according to  claim 3 , further comprising: 
       an oxygen partial pressure-detecting means for decomposing said predetermined gas component contained in the measurement gas after being pumping-processed by said pumping means, by means of catalytic action, and generating an electromotive force corresponding to a difference between an amount of oxygen produced by said decomposition and an amount of oxygen contained in a reference gas, wherein:  
       the predetermined gas component contained in said measurement gas is measured on the basis of said electromotive force detected by said oxygen partial pressure-detecting means.  
     
     
       6. The gas sensor according to  claim 1 , wherein said substrate is substantially planar and said at least one dimension of said slit passage extends generally perpendicular to the plane of said substrate. 
     
     
       7. The gas sensor according to  claim 1 , wherein said substrate is substantially planar and said at least one dimension of said slit passage extends generally within the plane of said substrate. 
     
     
       8. A nitrogen oxide sensor for measuring an amount of a nitrogen oxide component contained in a measurement gas existing in an external space, said nitrogen oxide sensor at least comprising: 
       a substrate composed of an oxygen ion-conductive solid electrolyte to make contact with the external space;  
       a first internal space formed at the inside of said substrate and communicating with the external space;  
       a gas-introducing port for introducing measurement gas from the external space into said first internal space;  
       a first diffusion rate-determining slit passage for introducing the measurement gas into said first internal space via said gas-introducing port under a predetermined diffusion resistance;  
       a clogging-preventive section provided between said gas-introducing port and said slit passage; and  
       a main pumping means including a first inner pumping electrode and a first outer pumping electrode formed at the inside and outside of said first internal space respectively, for pumping-processing oxygen contained in the measurement gas introduced from said external space, on the basis of a control voltage applied between said electrodes so that a partial pressure of oxygen in said first internal space is controlled to have a predetermined value at which NO is not substantially decomposable;  
       a second internal space communicating with said first internal space;  
       a second diffusion rate-determining slit passage for introducing an atmosphere pumping-processed in said first internal space into said second internal space under a predetermined diffusion resistance; and  
       a measuring pumping means including a second inner pumping electrode and a second outer pumping electrode formed at the inside and outside of said second internal space respectively, for decomposing NO contained in said atmosphere introduced from said first internal space, by means of catalytic action and/or electrolysis to pumping-process oxygen produced by said decomposition, wherein:  
       said amount of nitrogen oxide contained in the measurement gas is measured on the basis of a pumping current flowing through said measuring pumping means in accordance with said pumping process effected by said measuring pumping means;  
       at least one of said first and second slit passages has, when viewed in a plane substantially perpendicular to longitudinal extension axes thereof, two dimensions, and at least one dimension is not more than 10 μm; and  
       said clogging-preventive section has a cross-sectional area greater than that of said slit passage.  
     
     
       9. A nitrogen oxide sensor for measuring an amount of a nitrogen oxide component contained in a measurement gas existing in an external space, said nitrogen oxide sensor at least comprising: 
       a substrate composed of an oxygen ion-conductive solid electrolyte to make contact with the external space;  
       a first internal space formed at the inside of said substrate and communicating with the external space;  
       a gas-introducing port for introducing measurement gas from the external space into said first internal space;  
       a first diffusion rate-determining slit passage for introducing the measurement gas into said first internal space via said gas-introducing port under a predetermined diffusion resistance;  
       a clogging-preventive section provided between said gas-introducing port and said slit passage; and  
       a main pumping means including an inner pumping electrode and an outer pumping electrode formed at the inside and outside of said first internal space respectively, for pumping-processing oxygen contained in the measurement gas introduced from said external space, on the basis of a control voltage applied between said electrodes so that a partial pressure of oxygen in said first internal space is controlled to have a predetermined value at which NO is not substantially decomposable;  
       a second internal space communicating with said first internal space;  
       a second diffusion rate-determining slit passage for introducing an atmosphere pumping-processed in said first internal space into said second internal space under a predetermined diffusion resistance; and  
       an oxygen partial pressure-detecting means including an inner measuring electrode and an outer measuring electrode formed at the inside and outside of said second internal space respectively, for decomposing NO contained in said atmosphere introduced from said first internal space, by means of catalytic action to generate an electromotive force corresponding to a difference between an amount of oxygen produced by said decomposition and an amount of oxygen contained in a reference gas, wherein:  
       said amount of nitrogen contained in the measurement gas is measured on the basis of said electromotive force detected by said oxygen partial pressure-detecting means;  
       at least one of said first and second slit passages has, when viewed in a plane substantially perpendicular to longitudinal extension axes thereof, two dimensions, and at least one dimension is not more than 10 μm; and  
       said clogging-preventive section has a cross-sectional area greater than that of said slit passage.  
     
     
       10. A gas sensor for measuring an amount of a measurement gas component contained in a measurement gas existing in an external space, said gas sensor at least comprising: 
       a substrate composed of a solid electrolyte to make contact with the external space;  
       an internal space formed at the inside of said substrate;  
       a gas-introducing port for allowing gas communication between the internal and external spaces;  
       a clogging-preventive section positioned adjacent said gas-introducing port and having at least one dimension substantially the same as that of said internal space;  
       a diffusion rate-determining slit passage for introducing the measurement gas from the external space via the gas-introducing port under a predetermined diffusion resistance; and  
       a pumping means including an inner pumping electrode and an outer pumping electrode formed at the inside and outside of said internal space respectively, for pumping processing oxygen contained in the measurement gas introduced from the external space, on the basis of a control voltage applied between said electrodes, wherein:  
       said slit passage has, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, and at least one dimension is not more than 10 μm; and  
       said clogging-preventive section has a cross-sectional area greater than that of said slit passage.